Jon Cohen: 5 myths about political polls

When Mitt Romney was trailing in public polls before the first presidential debate – particularly in swing states – his campaign manager was dismissive, contending that, according to his camp’s superior internal data, the race was “inside the margin of error.” After the debate, when Romney grabbed the advantage in some public surveys, it was the Obama campaign arguing that “polls don’t matter.” Well, polls do matter. And it matters how they’re conducted and scrutinized. When trying to make sense of the numbers, here are a few myths to keep in mind.

When Mitt Romney was trailing in public polls before the first presidential debate – particularly in swing states – his campaign manager was dismissive, contending that, according to his camp’s superior internal data, the race was “inside the margin of error.” After the debate, when Romney grabbed the advantage in some public surveys, it was the Obama campaign arguing that “polls don’t matter.” Well, polls do matter. And it matters how they’re conducted and scrutinized. When trying to make sense of the numbers, here are a few myths to keep in mind.

• Myth No. 1: A campaign’s internal polls are more accurate than public polls.

The message from both sides, when they’re slumping, is consistent: Campaign polls are better at assessing voters’ intentions than the polls produced by news organizations and universities.

But there is a central flaw in private polling, at least what we get to see of it: Most campaign surveys are presented with a heavy dose of spin. The goals are also different, with a premium on testing messages and anticipating the effects of strategic decisions, often with tenuous assumptions about “likely voters” that may prove wrong.

Nor are campaigns reliable interpreters. Testifying under oath in the trial of former presidential contender John Edwards, Harrison Hickman, Edwards’ onetime pollster, said that the campaign used public polls as “propaganda.” Even though he privately counseled that Edwards had almost no chance of winning the 2008 Iowa caucuses, he said he monitored all the polls and sent “the ones that were most favorable because campaign aides wanted to share them with our supporters.”

“Out of a big stack of acorns,” Hickman said, “I was trying to pick out a few good ones that they could pass along to other people, you know, to keep them working.”

Immediately after the debate, coverage focused on polls that moved in Romney’s direction. After all, a Gallup survey showed that 72 percent of debate watchers said Romney did a better job, the most lopsided debate readout Gallup has ever recorded.

But there was little evidence that the debate decisively moved the needle in key swing states. In six state surveys released last week by two well-regarded polling partnerships – NBC-Wall Street Journal-Marist and CBS-New York Times-Quinnipiac – there were virtually no shifts for either candidate compared with pre-debate polls.

Nationally, the debate effect may have quickly faded. In Washington Post-ABC News polling after the candidates’ first face-off, voters had more positive reactions to Romney on the first two nights after the debate than on the next two. In Gallup tracking, the post-debate tally was nearly identical to what it was in the preceding days.

The presidential race has long been characterized as tightly competitive and voters as overwhelmingly locked in. The first debate seemed to do little to alter these basic, well-documented story lines.

• Myth No. 3: The best polls are those that correctly predict an election’s outcome.

Getting elections “right” is a necessary but insufficient reason to put great stock in polls. Some surveys could be well-modeled – adjusted to previous elections or to hunches, including, some surmise, tweaks to agree with other polls. (Few pollsters relish being an outlier.)

Both the Republican-leaning Rasmussen Reports and the Democratic-leaning Public Policy Polling have track records that some view favorably, but both use automated phone calls with recorded voices to collect data (“Press 1 for Obama, 2 for Romney,” etc.), revealing a basic flaw: It’s against federal law to have computers dial cellphones, so most “robo-polls” ignore about 30 percent of U.S. adults.

At a minimum, excluding cellphones means these polls are increasingly reliant on statistical weighting. They might make up for a lack of young people, for instance, by counting several times the answers from the few younger respondents. Peter Miller, a recent president of the American Association for Public Opinion Research, points out the root problem with weighting: “The more you rely on weights, the more you risk being wrong for reasons you don’t understand.”

It is always better to look at polls’ methodology, not just their results. What’s more, the “horse race” findings are often among the least important parts of a good poll. What issues motivate voters? And who is motivated to vote? These are more crucial to understanding an election than whether a candidate is up 2, 3 or 6 percentage points.

Political junkies quickly scan each poll release to see the “party ID split” – the proportions of self-identified Democrats, Republicans and independents in the sample. It makes sense: With party loyalty as strong as it is, the numbers of Democratic and Republican respondents in a survey make a huge difference. But to think, as many do, that there should be equal numbers from each party is off-base, particularly when looking at polls meant to assess the general population’s views.

Though voters seem split down the middle, there have generally been more Democrats than Republicans in the country since pollsters started tracking partisan allegiances after World War II. There is often more parity in election tallies, as Republicans tend to be more reliable voters than Democrats, but that also depends on the year.

Artificially evening out a poll’s partisan balance or arbitrarily setting it to match someone’s guess at turnout on Election Day may make one side a bit happier – but at the expense of distorting the current state of play.

Media-bashing is at a peak among conservatives, and some on the right routinely dismiss any poll showing Obama ahead of Romney. (And some on the left reflexively scorn polls in which Romney leads.) Before recent surveys turned in Romney’s direction, one conservative blogger went so far as to set up UnskewedPolls.com, a site offering “adjusted” public polls, tilted to favor Romney by manipulating the samples to be more Republican.

In truth, news organizations have only one bias – toward news.

Nothing demonstrates this better than the recent coverage of the Pew Research Center’s post-debate national poll, which showed big, across-the-board movements from Obama toward Romney. The Washington Post splashed the poll on its front page, and the survey provided days of fodder for cable news, illustrating that the media gravitate toward a competitive race, big shifts and conflict much more than one political party or the other.